JPH02295573A - Short range golf ball - Google Patents

Abstract

PURPOSE:To sufficiently suppress the range of a golf ball by providing a project ing part in an optimum shape protruding upward in the shape of a circuling arc in the bottom part of a circular dinple. CONSTITUTION:In the bottom part of a dinple 10 for the golf ball, a projecting part 11 is formed protruding upward in the shape of the circular arc. When a diameter in the maximum diameter of the projecting part is defined as D1 and a diameter in the outer edge of the dinple is defined as D2, in the condition of L=D1/D2, the size of the projecting part 11 is set so that the condition of 0.1<=L<=0.9 can be established. When the height of the projecting part is defined as H1 and the virtual maximum depth of the dinple recessed in the shape of the circular arc, in the condition of K=H1/H2, the size is set so that the condi tion of 0.6<=K<=1.0 can be established. The total number of the dinples is set in the range of about 250-600. As a result, the range of the golf ball can be enough suppressed. Since mold working to use an end mill system can be easily executed, the shape of the dinple can be made uniform.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a low flight distance golf ball, and in particular, to a method in which the shape of dimples is formed to increase the drag coefficient to suppress the flight distance of the golf ball. be.

As is well known in the art, dimples are provided on the surface of a golf ball in order to increase the lift coefficient and reduce the drag coefficient to increase flight distance when the ball flies. ing.

Golfers are demanding balls that fly well even at 1 yard, and for this reason golf balls are being improved with the aim of increasing flight distance, and dimples have also been improved to increase flight distance as much as possible.

However, recently, there has been an increasing demand for golf balls with reduced flight distance in the following two cases.

That is, in the first case, there is a problem that in a golf driving range called "all-out", the area of the driving range cannot be made sufficiently large, and the ball hit by the golfer ends up flying out of the driving range. In order to solve this problem, a golf ball with reduced flight distance is required.

In the second case, there is a desire to suppress the flight distance of the ball in order to enjoy the game using a long-distance club such as a driver even on a course where the distance from the teeing ground to the green is short.

Conventionally, as a method of suppressing the flight distance of a golf ball, Japanese Patent Application Laid-Open No. 1983-1989 2780 changed the formulation of the golf ball to lower the coefficient of restitution, suppressing the initial velocity of the ball at launch and increasing the flight distance. Method of suppressing
A method proposed in No. 683 is to provide a convex dimple to increase the drag coefficient of the ball during flight to reduce flight distance.

Problems to be Solved by the Invention The golf ball of JP-A No. 60-92780 has a flight distance of 5% less than a normal golf ball, and effectively prevents the problem of the ball flying out of the driving range net. However, it is not enough to use a driver on short holes on a golf course, and a further reduction in flight distance is desired.

In addition, the golf ball with convex dimples disclosed in JP-A No. 61-154683 has a much shorter flight distance than a normal golf ball, and has fully achieved its purpose in terms of reducing flight distance. Due to the mold processing and ball manufacturing process, there is a large variation in the shape of the individual dimples, which does not provide uniform flight performance and has an unfavorable appearance.

That is, to create a golf ball mold, first, a master male mold is created, and a hemispherical female mold is created from this male mold.
Generally, a combination of two of these hemispherical molds is used for molding golf balls. Most commercially available golf balls have concave dimples IA as shown in FIG.
To mold A, first a female mold 2 having a convex dimple 1B as shown in FIG. 9 must be provided.
In order to create the female mold 2, it is necessary to mold a male mold 3 having concave dimples 1C as a master as shown in FIG. The male mold 3 having such a concave dimple IC can be produced by preparing a plain hemispherical mold and cutting dimples into it with an end mill having an appropriate shape, which is relatively easy and requires a small number of Dimple IC can be processed within the error range.

On the other hand, as shown in FIG.
In order to mold the golf ball having the convex dimples IIA of No. 1, it is necessary to provide a female mold 5 having concave dimples 4B as shown in FIG. It is necessary to mold using a male die 6 having a convex dimple 4C as shown in FIG.

However, in order to create the male die 6 having the convex dimples 4C, elaborate equipment such as electrical discharge machining is required, which increases the cost and reduces machining accuracy, resulting in variations in the dimple shape. As a result, golf balls with convex shapes have a problem of inconsistent flight performance. Furthermore, as mentioned above, since golf balls are molded by fitting two hemispherical molds together, cracks inevitably occur on the mating surfaces of the upper and lower molds, that is, on the parting line. . This paris is polished with a grindstone, but in a golf ball having convex dimples 4A as shown in FIG. A portion of the dimples in the first row adjacent to are shaved and deformed. As a result, golf balls having such convex dimples have a problem of poor appearance and variation in flight performance.

The present invention has been made in view of the above-mentioned problems with conventional low-flying distance golf balls, and the dimples are shaped so that the flying distance is sufficiently suppressed, and the dimples can be easily manufactured without variation. It is an object of the present invention to provide a golf ball that has less variation in flight performance and has a good appearance.

Means for Solving the Problems In order to achieve the above object, the golf ball according to the present invention has a convexity that protrudes upward in an arc shape at the bottom of the concave dimple in order to increase the drag coefficient and suppress the flight distance. It is characterized by forming a part.

That is, in the present invention, at the bottom of the dimple of the golf ball,
Assuming that a convex portion protruding upward in an arc shape is formed, and the size of the convex portion is L=Dl/D2, where the maximum diameter of the convex portion is DI, and the diameter of the outer edge of the dimple is D2, 0.1 ≦ K ≦ 09 And when the height of the convex portion is Hl, the virtual maximum depth of the arc-shaped dimple is H2, and K=H1/H2, 0.6 ≦ K ≦ 1. 0 and the total number of dimples is about 250 to 6.
00 golf balls.

By forming a convex portion at the bottom of the concave dimple as described above, it is possible to increase the drag coefficient during flight of the golf ball, as will be revealed in the experimental results described below.
Flight distance can be suppressed.

Further, the processing of the dimple to form a convex portion at the bottom of the above-mentioned concave dimple is performed by cutting a master male die by cutting with an end mill, in the same manner as for the normal concave dimple shown in Figs. 8 to 10. can. The machining of the master is easy, and it is possible to improve the machining accuracy and make the dimple shape uniform, thereby reducing the variation in flight distance of the low flight distance golf ball.

Further, in the golf ball of the present invention in which a convex portion is formed at the bottom of the dimple, the parting line on the parting line can be polished without cutting the dimple, and the appearance is not deteriorated and variations in flight performance are reduced. I can do it.

Below, the present invention will be explained in detail with reference to embodiments shown in the drawings.

FIG. 1 shows an enlarged part of the golf ball according to the present invention, where IO is a dimple and 1l is a dimple 10.
A convex part protruding in an arc shape at the bottom of the , l2 is a dimple IO
The outer edge 13 is the outer edge surface of the portion where the dimple IO is not provided.

The dimple 10 is a recess formed as a part of a perfect circle in cross section, and with the lowest end position of the dimple 10 as the center,
Similarly, a convex portion +1 having a shape constituting a part of a perfect circle in cross section is integrally provided. The convex portion II must be set to an appropriate size; if it is too small, it will not be effective, and if it is too large and protrudes from the spherical surface of the dimple pole, there will be a problem when deburring the parting line. Therefore, based on the experimental results, the range is set as below. That is, the maximum diameter of the dimple l1 is D1, and the diameter of the outer edge of the dimple lO is D2.
If L=Dl/D2, it is set as 0.1≦L≦0,9.

In addition, when the height of the convex portion II is H1, the virtual maximum depth of the dimple provided in an arc shape is H2, and K=H1/H2, it is set to 0.6 ≦K≦ 1,0. .

A large number of the dimples 10 described above are provided as schematically shown in FIG. 2, and it goes without saying that dimples 10 having the same shape may be provided in various sizes by changing the diameter. The total number of dimples on one golf ball is approximately 25.
The range is from 0 to 600.

The golf ball having the dimple 10 having the convex portion l1 is molded by combining two hemispherical female molds l5 shown in FIG. 3, and the female mold 15 is a male mold shown in FIG. I6 is being created and molded. The mold surface of the female mold l5 is provided with a convex part 2l having a concave part 20 at the tip in order to mold the concave dimple 10 having the convex part l1, and thus forms the mold surface of the female mold l5. For male type! 6 is provided with a recess 23 having a protrusion 22 at the bottom. The recessed portion 23 of the male die 16 is formed by cutting with an end mill, similarly to a normal male die of a concave dimple.

The reason for setting the value of L above as 0.1≦L≦0.9 is that if it is less than 0.1 or exceeds 0.9, the tip shape of the end mill used will become too sharp. This is because it becomes impossible.

Furthermore, the reason why the value of K is set to 0, 6≦K≦1.0 is because if K is less than 0.6, the convex portion 11 will become too small, and the effect of providing the convex portion ll will be lost. This is because it becomes insufficient to suppress flight distance.

On the other hand, if K exceeds 1.0, machining of the male mold 16 using an end mill becomes impossible, and the aforementioned electrical discharge machining or the like must be relied upon.

In addition, if K7><1.0, the tip of the convex portion 11 will protrude from the spherical surface of the pole, and as noted above,
Polishing of the holes on the parting line becomes difficult, and the convex portions of the first row of dimples adjacent to the parting line are shaved off during polishing. In that case, the uniformity of the dimples will be lost and the flight performance of the golf ball will vary. Furthermore, if the ball protrudes beyond KI11.0, when actually used,
This is because the tip of the protruding convex portion l1 is scraped off due to repeated hitting with the club.

Also, the reason why the number of dimples is set from 250 to 600 is because, as is well known, if the number is less than 250 or more than 600, no lift will be generated during the flight of the ball, resulting in a liner-like ball. It is from.

In order to demonstrate the flight distance and symmetry of the golf ball according to the present invention described above, a golf ball having the structure of the present invention,
A conventional golf ball and a golf ball having a K value different from the range of the present invention were prepared as shown in Table 1 on the next page.

As shown in Table 1, golf balls of Examples 1 and 2 according to the present invention, Comparative Example 1 with a conventional structure, and Comparative Examples 2 and 3 whose K value range is not within the range of the present invention are provided. . The dimple patterns of these golf balls all have an icosahedral arrangement as shown in FIG. 5, and the number of dimples is 392. The dimple volume listed in Table 1 is the volume of the portion indicated by the diagonal line S on the sixth tooth,
Measured with a surface roughness meter. The sum of the volumes of each dimple is the total dimple volume, which is unified to 320±2 mm'. The structure of the golf ball is a wound ball with a balata cover, and the compression is uniformly 95±2.

Example! Example 2 is a ball with a convex portion at the bottom of the dimple so that the K value is 0.6, and Example 2 has a K value of 0.6.
This is a ball with a convex portion of 8.

Comparative example! is a ball with a normal concave dimple without a convex portion at the bottom of the dimple.

Comparative Example 2 is a ball in which a convex portion is provided at the bottom of the dimple so that the K value is 0.5, and Comparative Example 3 is a ball in which a convex portion is provided so that the K value is 1.1.

The L value in both Examples 1 and 2 and Comparative Examples 2 and 3 was 0.
The protrusions are provided so that the number is 5.

Further, the male molds described above for molding the balls of Examples 1 and 2 and Comparative Examples 1 and 2 were processed using an end mill method. Therefore, the dimples of these balls have less variation in appearance.

In addition, the finished ball has a good polishing pattern on the parting line, making it a ball with a beautiful appearance.

On the other hand, in the male die for molding the ball of Comparative Example 3, the dimples are formed by electric discharge machining, and therefore, the individual dimples have large variations in appearance. In addition, the finished ball has insufficient polishing of the edges on the parting line, and when polishing the edges, the convex part of the first row of dimples adjacent to the parting line is shaved off, resulting in an unfavorable appearance. It has become a thing.

"Experiment example l" Experiment example! , 2 and Comparative Examples I, 2, and 3 were tested for flight distance using a swing robot manufactured by Tsuru Temper Co., Ltd. with a driver at a head speed of 45 m/s.

The results are shown in Table 2 on the next page. The numerical values in Table 2 are the average values of the results of testing 12 golf balls of each type. Wind conditions on the day of the test were 1.5 to 3.0 m/s. Launch angle of this test was around 9.7 degrees, spin was 3600 rpm.
The following launch conditions are average conditions for a golfer with a head speed of 45 m/s.

The trajectory height in Table 2 is the elevation angle of the highest point of the trajectory as seen from the ball launch location.

The relationship between the K value and the total flight distance in Table 2 above is as shown in the graph of FIG. As shown in the graph, it can be seen that the higher the K value is, the lower the total flight distance is, and it can be seen that the total flight distance is extremely reduced when the K value is 0.5 as the boundary.

That is, as shown in Table 2, the golf pole of Comparative Example 2 with a K value of 0.5 has a total flight distance that is only slightly less than 3% lower than that of Comparative Example I with a K value of O. Comparative example 3 with K value of 1.1
Although the total flight distance has been significantly reduced, as mentioned above, due to processing problems, the appearance of the dimples is unfavorable and the flight performance is inconsistent.

On the other hand, the golf balls of Example 1 with a K value of 0.6 and Example 2 with a K value of 0.8 had a total flight distance of 13%, respectively, compared to the golf ball of Comparative Example 1 with a K value of O. ! 7
% has decreased.

This experiment was conducted at a head speed of 45 m/s, but considering that the average golfer's head speed is 40 to 45 m/s, when using the golf balls of Examples 1 and 2, Even on short holes,
You can play with a driver in Tisisit.

"Experimental Example 2" The golf balls of Experimental Examples 1, 2 and Comparative Example 3 were used with a driver at a head speed of 48.8 m/s using a swing robot manufactured by Tsuru Temper Co., Ltd., in order to examine variations in flight performance. A symmetry test was performed.

The results are shown in Table 3 on the next page.

In Table 3, seam hitting is a method of hitting the ball so that the axis of backspin is the line connecting the north and south poles when the parting line is regarded as the equator of the globe. Also,
Ball hitting is a method of hitting a ball so that the axis of rotation of seam hitting and a line perpendicular to the center of the ball serve as the axis of rotation of backspin.

The numbers in Table 3 are 20% when hitting each type of golf ball with a pole.
This is the average value of the results of 7 tests of 20 pieces and seam shots. The wind conditions at this time were almost calm.

As shown in Table 3, the golf ball of Example 1 with a K value of 0.6 and the golf ball of Example 2 with a K value of 0.8 have a high flight distance and trajectory height between ball hits and seam hits. There is almost no difference in flight time. In other words, it can be said that this is a golf ball with little variation in flight performance. On the other hand, K value h month. The golf ball of Comparative Example 3 of Comparative Example 3 had a large difference in flight distance, trajectory height, and flight time between hitting the ball and hitting the ball, and had large variations in flight performance. The reason why there is a large difference between the ball hit and the seam hit with the golf ball of Comparative Example 3 is that the dimple effect of the seam hit is weakened due to the unscraped paris on the parting line and the scraped dimple in the 1st row of the parting line. This is thought to be due to a decrease in the lift coefficient and a lower trajectory height.

Effects of the Invention As is clear from the above explanation, the low flight distance golf ball according to the present invention has an optimally shaped convex portion at the bottom of the concave dimple, so that the flight distance can be sufficiently suppressed. . Furthermore, since molding using an end mill method is easy, it is possible to make the dimples uniform in shape.

In addition, polishing of the edges on the parting line can be done reliably without affecting the dimples, so there are no variations in flight performance, and there are advantages such as a good appearance.

[Brief explanation of the drawing]

FIG. 1 is an enlarged view of Ichiro showing the dimple shape of the golf ball according to the present invention, FIG. 2 is a schematic diagram showing the entire golf ball of the present invention, and FIG. 3 is a diagram showing the process for molding the golf ball shown in FIG. FIG. 4 is a schematic diagram showing a male mold for forming the female mold of FIG. 3, and FIG. 5 is a schematic diagram showing Examples 1, 2 and a comparative example! , 2 and 3 are front views showing the dimple patterns of the golf balls of the present invention, FIG. 6 is a partially enlarged view showing the portion corresponding to the dimple volume of the golf ball of the present invention, and FIG.
The figure is an example of the present invention! , 2 and comparative example! , 2 and 3. Figure 8 is a schematic overall view of a conventional golf ball with concave dimples. Figures 9 and 10 are diagrams showing the results of the golf ball shown in Figure 8. FIG. 11 is a schematic diagram showing the female type and male type of the golf ball, FIG. 11 is a schematic overall view of a conventional golf ball having convex dimples, FIG.
Figure 3 is the first! FIG. 2 is a schematic diagram of a female mold and a male mold for molding the golf ball shown in the figures. 10... dimple, 1l... convex part. Patent applicant Sumitomo Rubber Industries, Ltd.

Claims (1)

[Claims] 1. A convex portion projecting upward in an arc shape is formed at the bottom of the dimple of the golf ball, and the size of the convex portion is set such that the maximum diameter of the convex portion is D1, and the outside of the dimple is If the diameter of the edge is D2 and L=D1/D2, then 0.1≦L≦0.9, the height of the convex part is H1, and the virtual maximum depth of the dimple formed in an arc shape is H2. , when K=H1/H2, it is set to 0.6≦K≦1.0, and the total number of dimples is about 250 to 6.
A low flight distance golf ball in the 00 range.